Several different types of membraneless particle separation devices having a generally spiral or curved configuration have been described in U.S. patent application Ser. No. 11/606,460, filed Nov. 30, 2006, entitled “Particle Separation and Concentration System,” U.S. patent application Ser. No. 11/936,729, filed Nov. 7, 2007, entitled “Fluidic Device and Method for Separation of Neutrally Buoyant Particles,” U.S. application Ser. No. 11/936,753, filed Nov. 7, 2007, entitled “Device and Method for Dynamic Processing in Water Purification,” and co-pending, commonly assigned U.S. patent application Ser. No. 12/120,153, filed on even date herewith, entitled “A Method and Apparatus for Splitting Fluid Flow in a Membraneless Particle Separation System,” and naming Lean et al. as inventors.
In general, such devices are useful in connection with particles having density differences compared with water, thus creating centrifugal or buoyancy forces necessary for transverse migration through the channel for purposes of separation. Some of these devices are also useful, depending on their configuration, to separate neutrally buoyant particles.
With reference to FIG. 1, one example form of a separation device 20 is shown. This form shows an expanding spiral channel 22 with increasing radius of curvature. This geometry takes advantage of the rate of pressure change. Other configurations may also be used. In another form, the device may have a contracting spiral channel with a decreasing radius of curvature for the sidewalls. The radius of curvature and channel size may also be held substantially constant. In any case, the channel 22 evolves into two separate channels 24 and 26 (e.g. also referred to as channel #1 and channel #2 in FIG. 1) to provide two outlet paths for the fluid.
These types of separation devices provide for particle separation in a variety of manners. For example, depending on the flow rate, the particle separation may be driven by the centrifugal force or the pressure that is created by flow fluid through the channel. In any event, it is the objective of such devices to achieve particle separation. In this regard, homogeneously distributed particles at the inlet are separated into a band, or populated in a portion of the fluid stream, and diverted at the outlet into a first portion or band including selected particulates and a second portion without such particulates resident therein. Co-pending, commonly assigned U.S. patent application Ser. No. 12/120,153, filed May 13, 2008, entitled “A Method and Apparatus for Splitting Fluid Flow in a Membraneless Particle Separation System,” and naming Lean et al. as inventors, describes a variety of mechanisms and subsystems to enhance the splitting of the fluid flow at the outlet to provide enhancement for at least two outlet paths for the fluid.
Designs and implementations of these types of devices for different environments and incorporating selected improvements are desired.